Tools · demurrage & detention

Two clocks. Most people only watch one.

Demurrage runs while the container sits inside the terminal. Detention runs from the moment it leaves until you hand the empty back. They have different free days, different per-diem rates, and they overlap — which is how a shipment that looked fine turns into a four-figure invoice. Enter three dates and see both.

Run both clocks → All four tools Track shipments
2
Clocks, not one
Live
Accrual while running
£0
To find out
Your
Tariff, not ours
The exposure · /api/demurrage

Discharge, gate-out, empty return. That's the whole input.

Leave a date blank if it hasn't happened yet — that clock is still running and the tool shows it accruing, plus how many free days you have left. The per-diem tiers below are editable: put your own carrier tariff in and the answer becomes yours rather than ours.

Container discharged from the vessel. Starts the demurrage clock.
Container left the terminal. Stops demurrage, starts detention. Blank = still at the port.
Empty handed back to the carrier. Stops detention. Blank = still out.
Charges are per container, per day.
From your bill of lading or carrier contract. Varies by carrier, port and trade.
Often longer than the demurrage allowance, and counted separately.
Per-diem tariff — replace the assumed rates with your carrier's actual tariff

Both charges are tiered — the daily rate steps up the longer the box is held. The values pre-filled here are the calculator's assumed defaults, not a carrier quote. Your bill of lading has the real ones. Change them and the result recalculates against your tariff.

Demurrage — £ per container per day
Detention — £ per container per day

Indicative · the carrier tariff and local port rules set the real free days + per-diem · decision support, not an invoice

The honest version

What decides the real number.

the authority

The carrier tariff wins

Free days and per-diem rates come from your bill of lading and the carrier's published tariff, and they differ by carrier, port, trade lane and equipment type. This tool computes your inputs correctly — it does not know your contract.

watch for

Calendar days, not working days

Most tariffs count calendar days including weekends and bank holidays, which is why a Friday discharge is worse than a Monday one. Some ports also apply their own separate storage charge on top of carrier demurrage.

the trap

The empty return is the forgotten leg

Detention keeps running after you've unloaded and moved on. If the depot is full or the haulier can't get a slot, the clock doesn't care. That's the charge that most often arrives as a surprise.

what to do

The cheapest day is the one before

The value here is pre-emptive: knowing on day three that you have two free days left is worth far more than reconciling the invoice six weeks later. That's what "accruing" and "free time left" are for.

FAQ

What's the difference between demurrage and detention?
Demurrage is charged for the container remaining inside the terminal beyond its free time. Detention is charged for the container being outside the terminal — in your yard, at your warehouse, anywhere — beyond a separate free-time allowance, until the empty is returned. One shipment can incur both.
Where do the pre-filled rates come from?
They're the calculator's assumed default tiers, shown openly so you can see exactly what's driving the number — not a quote and not any carrier's published rate. Open the per-diem tariff panel and replace them with the figures from your bill of lading.
Can I use this to dispute an invoice?
It's decision support, not an invoice or an audit. It will tell you whether a charge looks consistent with the dates and the free days you were given, which is a reasonable starting point for a conversation with your carrier — but the carrier's tariff and the terminal's records are the authority.
What if a date hasn't happened yet?
Leave it blank. That clock is treated as still running: you get the exposure accrued so far, an "accruing" flag, and the number of free days remaining before charges start. Re-run it any day for an updated position.
Indicative decision support, not an invoice. The carrier's tariff sets the real free days and per-diem.